EXTKACTIVE AND SALTS. 221 



reached in the forenoon. Exercise to a moderate degree does not seem 

 to influence it, though that of a more violent kind, and also mental ex- 

 citement, do. Fasting for one day does not diminish it. Copious 

 drafts of water increase it, but it subsequently declines. The admin- 

 istration of sulphur, and of the sulphates of potash, soda, and magnesia, 

 also increases it, the latter salts being removed from the system through 

 the kidneys. 



The quantity of extractive matter excreted by children is much more 

 than that excreted by adults, when estimated, as all such Q uantit ofex 

 observations ought to be, by reduction to a common stand- tractive in 

 ard. Thus Scherer found that for every thousand parts of T 

 weight a child excreted 0.346 of a part of extractive per diem, but an 

 adult, for each thousand parts of weight, excreted 0.156 of a part, which 

 is less than half as much. . 



The quantity of chlorine in the urine, as chlorides of sodium and po- 

 tassium, undergoes many variations. Hegar shows that it y ariations in 

 is at a maximum in the afternoon, at a minimum in the the chloride of 

 night, and rising toward morning. Its quantity is increased Sl 

 after taking water, and then diminishes. Muscular exercise also in- 

 creases it. It is interesting to remark that, in inflammatory conditions 

 accompanied by copious exudations, the chlorides in the urine are so 

 much diminished that that secretion in its fresh state will yield no pre- 

 cipitate with nitrate of silver. In 80 cases of pneumonia observed by 

 Kedtenbacher, the acidified urine did not become turbid with nitrate of 

 silver, but as the inflammatory action subsided the chlorides reappeared. 



Of medicaments and other unusual substances introduced into the or- 

 ganism, those which are soluble in water, and have little Egca e of unu 

 affinity for the constituent matters of the body, are removed sual salts in 

 in the urine. In this list are found a great number of salts t] 

 which escape in this manner without undergoing any change ; such, for 

 example, as carbonate of potash, nitrate of potash, bromide of sodium. 

 Other substances undergo change previously to their elimination, as, for 

 instance, the alkaline sulphides, which become oxidized, and are then 

 finally removed as alkaline sulphates. Dr. Bence Jones has satisfactori- 

 ly shown that, when ammonia is taken, it is removed as nitric acid in the 

 urine. Under the administration of the neutral alkaline salts of vegeta- 

 ble acicls, alkaline carbonates in excess appear, owing to the oxidation 

 of their acid in the blood. That this is the true seat of the oxidation, 

 and that it takes place with great rapidity, is demonstrated by the in- 

 jection of such salts into the jugular vein, which very soon are found as 

 carbonates in the urine. 



When oxalate of lime is introduced into the stomach, it does not make 

 its appearance in the urine, perhaps because of its insolubility present- 



